Last I knew, if you use a spare you're supposed to:
1) Fuel it (regardless of how much is in the tank)
2) Sweep it (especially if a broom is ON the bus)
3) Regen it
None of those things were done by the previous driver on the spare I used today. A total lack of consideration for the coworker who will be the next user when you don't do those things.
As a result, I was on line with 2 buses (simultaneously) in the p.m., not having time to fuel either my own or the spare in the a.m. because number 3 above was not done. I will not say which spare or who was the previous driver because I know it applies to more than one.
(Thanks to the driver who eventually offered to take the spare to the pumps. Was working up a sweat running back and forth between the 2 buses ... LOL)